Final answer:
The perimeter of a square with a side length of 3ft is 12ft.
Step-by-step explanation:
The equation P = 4s represents the perimeter P of a square with side length s. To find the perimeter of a square with a side length of 3ft, you can substitute 3ft for s in the equation:
P = 4s
P = 4(3ft)
P = 12ft